Messages in this thread | | | Date | Fri, 21 Mar 2014 18:41:19 -0400 | From | Peter Hurley <> | Subject | Re: [PATCH resend] serial_core: Fix pm imbalance on unbind |
| |
Hi Geert,
On 03/21/2014 09:23 AM, Geert Uytterhoeven wrote: > Hi Peter, > > On Fri, Mar 21, 2014 at 2:06 PM, Peter Hurley <peter@hurleysoftware.com> wrote: >>> @@ -2681,10 +2683,12 @@ int uart_remove_one_port(struct uart_driver *drv, >>> struct uart_port *uport) >>> } >>> >>> /* >>> - * If the port is used as a console, unregister it >>> + * If the port is used as a console, unregister it, and power it >>> down >>> */ >>> - if (uart_console(uport)) >>> + if (uart_console(uport)) { >>> unregister_console(uport->cons); >>> + uart_change_pm(state, UART_PM_STATE_OFF); >> >> Won't this power off the port while tty consoles may still be open? > > I didn't see that actually happening.
Ok, but I still think this isn't right. See below.
>> I think the right thing here is to unregister_console then set uport->cons = >> NULL >> >> [uport->cons is properly reassigned when/if a port is re-added via >> uart_add_one_port()).] > > But indeed, for concistency/symmetry uport->state and uport->cons > should be resend, but that's something separate.
I don't see this as being a "looks good" problem; I see this as being "what's the right way to teardown a uart device that's going away when a tty console is running on it", and there are too many problems with uart_remove_one_port() doing:
state->uart_port = NULL
to keep with that solution.
>> Then, uart_close() will power off the port when all ttys using the port have >> been closed. > > uart_close() won't get that far, so uart_change_pm() won't be called.
And this is the central problem: uart_close() must complete normally if a tty console is still running on a device.
For example, if uart_shutdown() isn't getting called, then who's freeing the ring buffer page?
> See also https://lkml.org/lkml/2014/3/10/651, and my workaround for the > crash https://lkml.org/lkml/2014/3/17/231.
See my comments to the v2 patch there.
Regards, Peter Hurley
| |